Phytohormonal analysis of the resistance to Plum pox virus induced by grafting from almond to peach

Plum pox virus (PPV) is a limiting factor for peach production in those areas that are affected.
Although no natural sources of resistance have been described for peach, recent studies have demonstrated that grafting almond Garrigues onto GF305 peach seedlings heavily infected with PPV progressively reduces disease symptoms and virus accumulation.
This response appears to be specific between almond and peach.
Furthermore, grafting Garrigues onto GF305 before PPV inoculation completely prevented virus infection, showing that resistance is constitutive and not induced by the virus.
To unravel the phytohormonal basis of this mechanism, different plant hormones have been assayed including the cytokinin trans-Zeatin (tZ); the gibberellins GA3 and GA4; the abscisic acid (ABA); the jasmonates jasmonic acid (JA); the ethylene acid precursor 1-aminocyclopropane-1-carboxylic acid (ACC) and the salicylic acid (SA). First results showed the important implication of SA and cytokinin trans-Zeatin in the infection of the virus and the induced resistance in peach and almond.